Trouble with .sheet borders

Hello all,

I’ve got .sheet codes in my theme for the exterior border of all of my content (tl, tc, tr, etc.) and everything is working fine, with the exception of the tl (top left) and tr (top right) corners. It appears as if the PNG images that make up the corners aren’t even loading. I know they’re in the right place, and I’ve checked and double-checked the code, but I can’t figure out what is wrong. The site is located at blog.noelmarie.com and here’s the code for those specific functions:

.Sheet-tl
{
  position: absolute;
  overflow: hidden;
  z-index: -1;
  top: 0;
  left: 0;
  width: 16px;
  height: 16px;
  background-image:  url('images/Sheet-s.png');
}

* html .Sheet-tl
{
  font-size: 1px;
  background: none;
  behavior: expression(this.runtimeStyle.filter?'':this.runtimeStyle.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(src='" + (function(){var t=document.getElementsByTagName('link');for(var i=0;i<t.length;i++){var l=t[i];if(l.href&amp;&amp;/style\\.css$/.test(l.href))return l.href.replace('style.css','');}return '';})()+"images/Sheet-s.png',sizingMethod='crop')");
}

.Sheet-tr
{
  position: absolute;
  overflow: hidden;
  z-index: -1;
  top: -1;
  right: 0;
  width: 16px;
  height: 16px;
}

* html .Sheet-tr
{
  font-size: 1px;
  left: expression(this.parentNode.offsetWidth-16+'px');
}

.Sheet-tr div
{
  position: absolute;
  z-index: -1;
  top: 0px;
  left: -16px;
  width: 32px;
  height: 32px;
  background-image:  url ('images/Sheet-s.png');
}

* html .Sheet-tr div
{
  background: none;
  behavior: expression(this.runtimeStyle.filter?'':this.runtimeStyle.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(src='" + (function(){var t=document.getElementsByTagName('link');for(var i=0;i<t.length;i++){var l=t[i];if(l.href&amp;&amp;/style\\.css$/.test(l.href))return l.href.replace('style.css','');}return '';})()+"images/Sheet-s.png',sizingMethod='crop')");
}

Thanks for your help!